1. Field of the Invention
The present invention relates to a numerical controller, and more particularly to connection between a numerical controller and external signal input/output units.
2. Description of the Related Art
In an arrangement such that a plurality of external signal input/output units are connected to a numerical controller in order to input and output I/O signals (input/output signals) between a numerical controller and a machine tool, external signals (I/O) to be inputted and outputted vary depending on the configuration of a system. In inputting the I/O signals, it is necessary to freely allocate addresses in the numerical controller to the I/O signals.
In general, IDs (group IDs) for identification are set in units for external signals by means of switches on the units, the units are identified by the group IDs set by the switches (see JP 3297249B), and addresses are allocated to I/O signals based on the set group Ids.
According to the conventional method in which the group IDs for unit identification are set by means of the switches on the external signal input/output units, the IDs must necessarily be set with the switches on the individual input/output units at the time of connection between the numerical controller and the units and their maintenance. Thus, there is a possibility of setting errors. Since indispensable switching components are increased in number, moreover, the manufacture requires more inspection items, thereby entailing an increase in costs.
On the other hand, there is a possible method in which IDs are automatically allocated by software. According to this method, however, a wrong configuration cannot be detected at the time of system change, and an operation may possibly be performed with wrong allocation. Also in the case where the system configuration is temporarily changed at the time of maintenance, for example, the allocation of the addresses must inevitably be set again.